1. Field of the Invention
The present invention relates to a method and apparatus for converging motion image data, a method and apparatus for reproducing motion image data, a computer program for converting motion image data, and a computer program for reproducing motion image data, and more particularly, to a method and apparatus for converging motion image data, a method and apparatus for reproducing motion image data, a computer program for converting motion image data, and a computer program for reproducing motion image data, capable of performing high-quality data conversion such that motion image data is compressed with substantially no degradation in image quality, and capable of performing inverse data conversion such that high-quality motion image data is reproduced from compressed motion image data.
2. Description of the Related Art
When motion image data is stored on a storage medium such as a hard disk or a DVD or when motion image data is transmitted via a network, the motion image is generally compressed to reduce its data size. In recent years, a great improvement in quality of motion image data has been achieved. For example, an HD (High Definition) format is now available for representing high-quality motion image data. However, with improving in data quality, a drastic increase in the data size is occurring. To solve such a problem, a wide variety of techniques to improve efficiency in compression/decompression of motion image data and to prevent degradation in data quality due to compression/decompression are under development and evaluation.
A known technique to compress motion image data is spatial decimation to decimate pixels constituting an image frame of motion image data. Another known technique is temporal decimation to decimate frames (to reduce the frame rate).
By performing such data conversion, the data size can be reduced and thus it becomes possible to efficiently store data on storage medium or transmit data via a network. However, compression of data causes degradation in image quality. That is, data reproduced from compressed image data is not as good as the original data. The problem with degradation in image quality is serious, in particular, when original data is of a high-resolution image.
A wide variety of techniques have been proposed to reduce such degradation in image quality. For example, Japanese Unexamined Patent Application Publication No. 2003-169284 discloses an image compression technique in which parameters are set based on information indicating the brightness of an image, and a compression mode is switched depending on the brightness of the image. Japanese Unexamined Patent Application Publication No. 2002-27466 discloses an image compression technique in which a screen is divided into a plurality of regions, and an optimum compression mode is determined for each region.